Final answer:
Mr. and Mrs. Number are happy because they love arithmetic and enjoy working with numbers. The commutative property of addition states that the order of numbers being added does not matter. Arithmetic rules are universally valid and do not depend on time or location.
Step-by-step explanation:
The reason Mr. and Mrs. Number are so happy is because they love arithmetic. They enjoy working together with numbers and solving mathematical problems. They find joy in the process of addition, subtraction, multiplication, and division.
For example, the commutative property of addition states that A + B = B + A. This means that no matter the order in which numbers are added, the result will be the same. So, whether you add 2 + 3 or 3 + 2, the sum will always be 5.
Similarly, arithmetic rules are universally valid. It doesn't matter where you are or what time it is, the same mathematical rules apply. Whether you're in the 4th century BC or the 21st century, the rules of arithmetic remain the same.